Field
Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to wireless channel estimation.
Background
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
As the demand for mobile broadband access continues to increase, research and development continue to advance the UMTS technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications.
To ensure reception of wireless signals in a wireless environment, a wireless device may estimate a channel associated with a network entity, such as a base station. By estimating the channel, the wireless device may determine transmission characteristics of the transmitting base station, such as its timing schedule, signal phase, and other basic, necessary information. Typically, mobile devices estimate such channels by detecting, measuring, and processing a pilot signal transmitted by the network entity. In most wireless networks, this pilot signal is transmitted via a common pilot indicator channel (CPICH), which often serves as the exclusive basis for channel estimation and/or computing a related channel impulse response in legacy wireless communication systems and devices. In addition, these network entities often transmit a Primary Physical Common Control Channel (P-CCPCH), which is broadcast with a constant channelization code, slot format, and transmission time interval. The P-CCPCH contains important network parameter information that a mobile device may analyze before creating a dedicated connection with the network entity.
In some instances, the signal power of the CPICH is not strong enough when received by its set of client user equipment (UE) to allow each UE to perform reliable channel estimation based exclusively on the CPICH. Regardless of how weak the CPICH power may be in legacy systems, however, UEs of these systems continue to rely exclusively on the CPICH for channel estimation in spite of receiving a robust and predictable P-CCPCH.
Thus, because a weak received CPICH may not be powerful enough alone for some mobile devices to reliably estimate a channel, an improved method and apparatus for estimating a channel aided by the P-CCPCH is needed.